This invention relates generally to hypodermic needle assemblies and more particularly to a hypodermic needle assembly having a resilient, member-launched safety clip device for blocking the tip of a disposable needle after use to facilitate the safe handling of hypodermic needles.
Medical care of individuals requires the widespread use of needles for taking blood samples, intravenous drug delivery, and the introduction or removal of other fluids via cannula, needles, or syringes. In the current context, the use of hypodermic needles to deliver plasma, anesthetics, or other medications has become commonplace in medicine, science, veterinary medicine, and biotechnology. The use of a hypodermic needle typically involves first inserting a needle into the patient, injecting a substance or withdrawing a substance as required, and then removing the needle from the patient. In most applications, the withdrawn and contaminated needle must be handled very carefully during disposal to avoid needle stick injury.
To help prevent health care workers from becoming injured, guards have been developed to block the tip of these needles after use. Indeed, needle stick protection for medical professionals has become of particular importance in recent years because of the prevalence of potentially fatal infectious diseases, such as, for example, Acquired Immune Deficiency Syndrome (AIDS) and hepatitis, that can be transmitted by the exchange of bodily fluids through inadvertent wounds caused by accidental needle tip pricks after withdrawal from infected patients. Accordingly, many kinds of needle protection devices are available for providing post injection needle stick protection.
Devices which have been introduced to provide added protection against punctures by used needles fall into three basic categories, those which hide the withdrawn needle within a needle shield launched via a needle shield launching mechanism, those which require placement of a separate needle guard, and those which include a sliding shield which must be manually pushed along the needle shaft and over the tip of the used needle. Most of these needle guards are cumbersome and interfere with a single handed procedure, and or require additional complicated pieces to attach the needle guard to the needle tip.
Of the first type, i.e., devices which hide the withdrawn needle within a launched needle shield, there are several designs. However, all of these designs have undesirable features which make them unsuitable for many applications. For example, in one conventional design, a spring biased needle shield is provided which lockingly engages with the needle tip when the user manually activates the spring mechanism after the needle is withdrawn from the patient. However, while this mechanism provides for preventing the needle shield from disengaging and moving back down the length of the needle, the needle shields are only frictionally engaged to the tip of the needle, such that it is possible to slip the needle shield off of the distal end of the needle leaving the needle tip exposed. In addition, this design requires the user to manually activate the spring mechanism, which adds to the complexity of the design, manufacture, and use of the hypodermic needle assembly.
In another conventional design, the needle has a slightly expanded portion at the tip which prevents the needle shield from sliding off of the distal end of the needle once engaged. However, the needle shields utilizing this design still require the user to manually activate a second mechanism that then engages the needle guard, adding to the complexity of the design, manufacture and use of the hypodermic needle assembly.
Within this first category there are also a number of hypodermic needle assemblies for shielding the needle tip from being exposed once the needle is withdrawn from the patient which are automatically activated by the depression of the hypodermic plunger. However, the needle guards provided in most of these prior art designs consist of a simple hollow sleeve having an open distal end. While this design does provide protection from most inadvertent contact with the needle tip, it is still possible with such designs for a user to accidentally or purposefully insert a finger into the open distal end of the needle guard sleeve and thus come into contact with the contaminated needle tip.
Of the second and third types of needle shields, i.e., those which require placement of a separate needle guard or which use a shield that is manually pushed along a needle, there are several different designs. A number of these needle shields include either a spring-clip fitting or a frictional fitting, which are either placed directly on the tip of the needle or are movable from the base of the needle to the tip of the needle along the longitudinal direction of the needle. In the later embodiment, the user manually slides the needle shield toward the tip of the needle to thereby engage the needle shield around the needle tip. However, these manually activated designs require that the user either slide or apply the needle shield to the tip of the needle by hand, significantly raising the risk of unintentional contact with the needle tip.
Present day techniques thus offer a large number of solutions for protecting medical staff from used needles. However, as noted above, the known solutions suffer from at least one serious drawback. Accordingly, a hypodermic needle assembly is needed which reduces the risk of unintentional exposure of the used needle after use by automatically engaging the needle shield once injection is complete, without the need for additional complex mechanisms or cumbersome user operation.
According to the present invention, there is provided a hypodermic needle assembly designed such that the action of compressing the plunger of the syringe automatically activates a resilient, member-loaded needle shield such that the needle shield moves into position to block the needle tip, such that there is no risk of accidental injury and infection from an exposed needle and there is no need for the activation of any additional mechanisms to complete the needle shielding process.
The safety hypodermic needle assembly provided in accordance with practice of the present invention is a single-use device that is independent from the syringe assembly and is detachably attachable thereto. In one aspect, the safety hypodermic needle assembly comprises a needle hub having open proximal and distal ends, wherein the open proximal end defines a chamber configured to engage the tip of a syringe, and wherein the syringe tip has a plunger pin slidably mounted therein. A needle is provided which defines a longitudinal axis and has proximal and distal end portions. The distal end portion of the needle comprises a sharp needle tip, and the proximal end portion is mounted in the needle hub. The needle hub is configured such that the proximal end portion of the needle is in fluid communication with the syringe tip engagement chamber, and the distal end portion of the needle extends out from the distal end of the needle hub. A needle tip safety guard assembly is provided which comprises a needle tip safety guard which is mounted on the needle and arranged at the distal end portion of the needle hub. The needle tip safety guard assembly has a proximal end portion disposed within the open distal end of the needle hub, and the needle tip safety guard has a needle opening therein through which the needle extends. The needle tip safety guard assembly is configured such that when the needle tip safety guard is urged over the needle tip, the needle tip guard is engaged to block the needle tip. A needle guard activator assembly is provided for urging the needle tip safety guard in a distal direction along the needle. The activator assembly comprises a pressure trigger and a resilient member, wherein the pressure trigger is mounted in the needle hub and is arranged between the syringe plunger when the syringe tip is in the syringe tip engagement chamber and the needle tip safety guard, such that when the syringe plunger is translated distally, the plunger pin mechanically interacts with the pressure trigger. The pressure trigger is configured to transmit the force of the plunger pin longitudinally along the axis of the needle assembly in a distal direction, such that the resilient member is activated to urge the needle tip safety guard distally along the needle and over the needle tip to its blocking position. The needle tip safety guard is passively actuated so that the user is not required to perform any operations outside of those employed using conventional hypodermic needles. In order to use the safety hypodermic needle assembly, it is not necessary for the user to learn additional procedures. The needle tip safety guard automatically blocks the needle tip so that the user, or those who dispose of the used needle, are not subjected to inadvertent needle sticks.